A machine for the automatic punching-out of tin-can covers or lids from sheet-metal plates is known from the German Patent DE-PS 177,684. This machine includes a C-frame construction, wherein the press table including the mechanical sheet-metal plate processing device exhibit a position inclined by about 30 degrees, i.e. an inclined disposition of the press table relative to the horizontal. The main frame of the apparatus comprises a pair of C-shaped side cheeks and a strongly constructed so-called block is employed for supporting the table plate, wherein the block connects the pair of C-shaped side cheeks. The plate disposed on the feed device in the processing plane is led in longitudinal direction, i.e. from the front side toward the press feed opening, toward the table of the punching device and is then processed in transverse steps and longitudinal steps. The disadvantages of this press frame construction include obviously that, based on the spreading apart of the C-shaped frame upon cutting of sheet-metal plates, there exist narrow limits with respect to the tool life and the number of the tools which can be employed in the course of cutting of sheet-metal plates. In addition, a higher frequency of cutting sequences is hardly possible, since the smallest wear of contemporary tools already generates a damaging of the tools overall based on the stretching apart of the C-shaped frame. In addition, a generated cut edge burr at the tool pieces is a consequence of a wear of the tools and can lead to a prematurely required change of tools.
In addition, a laying and horizontally disposed C-frame press is known from the German Patent DE-PS 508,474, wherein the starting material plates pass to processing between two feed roll pairs disposed in a vertical position. The starting material plate is initially led and guided step-by-step and in sequence in the processing plant past a tool, disposed perpendicular to the laying and horizontally disposed press, wherein blanks are produced. Then, the scrap grate, generated during the cutting out of the blanks, is separately cut out by a scrap cutter from the residual starting material plate and is removed from the laying and horizontally disposed press.
The starting material plate, furnished with a new leading edge according to the process described above, passes thereupon between continuous belts, which continuous belts transport the just generated reduced material plate around the rear of the laying and horizontally disposed C-frame press to that side of the press, on which the feed roller pairs are disposed. Thereupon, a further row of workpieces or, respectively, scrap parts is separated from the plate. The disadvantages of this laying and horizontally disposed C-frame press comprise in addition that an expanding of the C-frame results in the already described disadvantages which have been pointed to in connection with the German Patent DE-PS 177,684. A further substantial disadvantage is recognized in the required large floor space requirement of the press with the feed advance device, wherein the continuous belts are in each case disposed laterally of the laying and horizontally disposed press table and have to be guided around the rear of the laying and horizontally disposed press head.
In order to increase the work-cycle frequencies at the conventional, inclinedly constructed C-frame press, one has moved in the past from the sheet-metal plate processing to the sheet-metal strip processing. In connection with the sheet-metal strip processing, the usual expanding of the C-frame press is substantially prevented by way of stud bolts, disposed left and right between the table and the side cheeks at the so-called press feed opening, wherein however the higher expenditure of the production sheet-metal strips requiring a sheet-metal strip cutter is knowingly accepted. This higher expenditure comprises further that a sheet-metal strip magazine has to be refilled relatively quickly based on the high operating frequencies.
Furthermore, plate processing devices at C-frame presses are also known, which perform the plate processing in a horizontal processing plane, as taught for example in the PCT document WO 94/08740. In this case, a horizontal table is furnished in front of the C-frame press, wherein the surface of the horizontal table is disposed in one plane together with the surface of the lower tool stand. At least a first cutting process for separating a work piece from the sheet-metal plate is performed on a sheet-metal plate, wherein the sheet-metal plate is fed from the side to the C-frame press and is moved through this C-frame press. The through-cutting and separation of the just generated cutting edges is performed in a second cutting process. Based on the C-frame press, the already described disadvantages occur, such as an expanding of the C-frame and the therewith associated premature wear problems, at the tools. On the other hand, the plate processing in a horizontal plane results in a larger floor space requirement.
The C-frame presses, in connection with which the invention apparatus for the sheet-metal process is to be employed, are known. In general, inclined presses of the type C-frame press are outfitted with so-called "pull anchors," whereby a frame elastic support, occurring during the stamping or press process, is prevented. It is however a disadvantage that these pull anchors, which are disposed immediately on the left-hand side and on the right-hand side at the operating region of the press, where the pull anchors connect the press main region with the press table region, allow only a feeding in and a processing of sheet-metal strips. These pull anchors prevent in general a processing of a plate. However, if the pull anchors are demounted, there results a press which offers the required space for a sheet-metal plate processing, where however the required rigidity of the press is no longer present. This rigidity is however an absolutely necessary prerequisite for the use of carbide-tipped tools in order that high stroke numbers and the least cutting burrs can be expected.
If such a C-frame press, which does no longer include pull anchors, is equipped with the invention apparatus, then entire plates can be processed since the required rigidity of the press can be assured with the apparatus according to the present invention.